Elevated temperature closed liquid heating systems



Jan. 16, 1962 ELEVATED TEMPERATURE CLOSED LIQUID HEATING SYSTEMS D. e. VANDENBURGH ETAL 3,016,835

Filed July 15, 1958 LOOSE INSOLUBLE PRODUCTS LOOSE. INSOLUBLE PRODUCTS INVEWTUiS DAVID GNANDENBURGH WAYNE W- BINGER BASIL M. PONCHEL QXM A ORAEV United States Patent Ofiflce Patented .lan. 16, 1962 ELEVATED 'lEMlEFRATURE CLflEiED LIQUll) i-iEA'lil lG SYSTEMS David G. Vandcnhurgh, Wayne W. Binger, and Basil M. Ponchel, New Kensington, Pa, assignors to Aluminum Company of America, Pittsburgh, Pa, a corporation of Pennsylvania Filed July 15, 1958, Ser. No. 743,666 2 Claims. (Ci. 1221i) This invention relates in general to closed liquid systems operating at elevated temperatures, and is more particularly addressed to closed hot water systems and storage vessel or tank structures employed therein.

The presence of loose insoluble deposits in the liquid media within closed liquid systems operating at elevated temperatures has been observed to be a source of erratic and objectionable functioning of such systems. For example, closed hot water systems incorporating storage stand tanks, with under-fired or heated bottom closure crown sheets, are known to develop objectionable rumbling noises during their operation, particularly when the aforesaid loose insoluble deposits are permitted to accumulate on the liquid side of the under-fired or heated bottom end closure crown sheets of the storage tanks employed in such systems.

Elevated temperature closed liquid systems, such as hot water supply systems, are normally designed to sup ply definite volumes or quantities of liquid within preselected temperature ranges in accordance with desired recovery rates. No appreciable difliculty has been encountered in meeting the aforesaid desirable characteristics except in cases where the previously mentioned loose insoluble deposits or residues are permitted to accumulate on the liquid contacting surface of under-fired or heated bottom closure crown sheets of storage tanks incorporated in such systems, in which latter case the capacity, temperature and recovery characteristics cannot always be obtained without experiencing the aforesaid objectionable rumbling noises in the systems, particularly when relatively large pressure variations are experienced in the operation of such systems.

An extended test program on commercial hot water storage tank systems has revealed the objectionable rumbling noise conditions, in the presence of the aforesaid deposits, long before reaching the desired liquid storage temperature at the manufacturers stated recovery specifications, and has further developed the fact that the accumulated loose insoluble deposits or residues in contact with the liquid side of the bottom end closure crown sheets of under-fired storage tanks were responsible for temperature readings on the liquid side of the bottom crown sheets beneath the residues in excess of the normal boiling point of the liquid in the storage tanks corresponding to the minimum operating pressures therein. These observed and recorded excess temperatures are considered to be the cause of the objectionable rumbling noises complained of, in that a drop in pressure on such systems, as by drawing water therefrom by opening a faucet, causes flash vaporization of the liquid or water beneath the accumulated residues, formation of vapor bubbles, and collapse of the same through condensation thereof in contact with colder water or liquid in the storage tanks.

The loose insoluble deposits in elevated temperature closed liquid systems, and particularly in hot water systems, are attributable to many sources, such as precipitation products, organic and inorganic salts and compounds, entrained solids in the liquid supply, and products of corrosion generated from the materials of the tanks, galvanic anodes and the piping employed in such systems.

The rumbling noise was eliminated in the aforesaid conducted test program by regulating the temperature of the bottom end closure crown sheets supporting the aforesaid insoluble deposits or residues in several commercial hot water storage tanks to some temperature below the normal boiling point of the water in the systems so tested corresponding to the particular minimum pressures on the systems. Such lowered heating temperatures were found to fall well below those recommended by the storage tank manufacturers to insure delivery of water at specified temperatures and recovery rates, thus resulting in under-capacity ineflicient equipment operation.

It is an object of the present invention to provide improved elevated temperature closed liquid storage and supply systems characterized by substantial freedom from objectionable rumbling noises in their normal operation, notwithstanding the presence of loose insoluble deposits in the storage tanks of such systems.

Another object of the invention is to provide holding or storage tank facilities in closed hot water systems in which normally under-fired or heated bottom closure. end crown sheets of the storage tanks have been modified to divert or deflect direct impingement of heat against the exterior surface of the crown sheets.

A significant object of the invention is to provide an elevated temperature closed liquid heating system incorporating an under-fired liquid storage tank, in which loose insoluble deposits have been permitted to accumulate on the liquid side of the end closure crown of the tank, which system, is substantially free from objectionable rumbling noise in the intended capacity, recovery and elevated temperature requirements of the system.

Other objects and advantages will be understood from consideration of the following description and drawing, in which:

FIG. 1 represents a typical lateral flue type elevated temperature liquid heating system and storage tank or vessel, in sectional elevation, incorporating features of the invention;

FIG. 2 represents a typical central flue type elevated temperature liquid heating system and storage tank or vessel, in sectional elevation, incorporating features of the invention; and

FIG. 3 represents a fragmentary sectional elevation of the bottom end portion of an elevated temperature liquid storage tank or vessel suitable for substitution in either of the structures of FIGS. 1 and 2.

Basically, the invention is addressed to hot water storage or holding tanks of the vertical stand boiler type which are normally under-fired or subjected to heat over a substantial area of their bottom or end closure crown sheets, but in which a heat deflecting media and/ or structure is interposed between the heat generating means and exterior exposed surface of the bottom end closure crown sheets of the storage tanks to deflect or divert direct impingement between products of combustion or high temperature air or gas and the exposed exterior bottom surface area of the tank end closure crown sheets. As a result of such tank construction, highly heated exposed bottom surface areas, which would otherwise result in the development of hot spots on the interior surfaces of the end closure crown sheets in supporting contact with loose insoluble deposits or residues, with accompanying rumbling noise, are avoided.

On reference to FIG. 1, a typical commercial hot water storage tank is illustrated as comprising a cylindrical or tubular metal body section It), a top end closure plate or crown sheet 12 and bottom end closure plate or crown sheet 14. The elements ll), 12 and 14 may be constructed from any suitable metal or metal alloy, with or without interior surface treatment to improve their corrosion resistance against water or other liquid media employed therein.

A lateral flue 16 is provided in surrounding relationship in respect of the main cylindrical body section Ilil of the tank, in accordance with standard practice, for conducting the hot gas and products of combustion upwardly along the exterior surface of the tank wall and ultimate discharge of the same into a stack venting to atmosphere.

It is a common expedient in mass fabrication of tanks in accordance with MG. 1 to employ upwardly dished top and bottom crown sheets 12 and M, respectively, to provide at least one flat end supporting surface for the tanks, riveting or welding techniques being usually employed in the assembly and construction of such cylindrical storage tank units.

in the usual installation and use of storage tanks of the type illustrated in FIG. 1 in not water or other elevated temperature liquid systems, the tank is connected into the cold water or low temperature liquid supply line 18, which preferably extends downwardly through the top crown sheet 12 to a distance preferably greater than two thirds the vertical depth of the tank. A hot water or other liquid draw-oil line 25 also preferably enters the tank through or adjacent its top crown sheet 12 and projects a short distance vertically into the tank.

The most common type of heater employed in elevated temperature closed liquid systems consists of a multiport, ring or annulus type burner 22 disposed below the bottom end closure crown sheet M. The burner 22 is usually provided with a plurality of burner jets directed towards the exposed under surface of the crown sheet 14. Any suitable fuel, such as gas, oil or mixtures thereof, is supplied under suitable pressure through a burner manifold 24. It will be understood that other types of fuel and burner structures, including electrical heating means, may be employed if desired.

Closed water systems similar to FIG. 1 are in regular use and are known to develop the objectionable rumbling noises heretofore referred to when accumulated loose insoluble deposits are permitted to collect on the interior surfaces of the bottom crown sheet i l.

To overcome the rumbling noises characteristic of the hot water systems and tank structures above described, a bottom pan-shaped shell 26 has been secured over the bottom or lower end 14 of the storage tank and is provided with a central panel 28 preferably, although not necessarily, conforming substantially to the underside curvature of the bottom crown sheet 14. The shell 26 is also preferably spaced below the underside of the bottom crown sheet 14 and is marginally flanged upwardly at 36 in spaced relationship to the cylindrical body portion it of the storage tank to a distance equal to or slightly above the depth of accumulated deposits in the bottom of the tank. The shell member 26 may be made from metallic sheet or ceramic material and its primary purpose is to serve as a deflector against direct impingement of flames and/or heat rays delivered by the burner 22 against the underside of the bottom crown sheet 14, as well as against the marginal end wall portion of the tank adjacent and in direct interior contact with the loose insoluble residues or deposits accumulated in the channel shaped groove formed at the juncture of the bottom crown sheet and tank wall. The space between the underside of the bottom crown sheet 14 and lower peripheral marginal end of the body of the tank 10 may, if desired, be filled with an insulating material 32, such as asbestos packing, glass wool, or similar insulating materials or mixtures thereof. Furthermore, the deflector sheet 26 may in itself be selected from a material exhibiting thermal insulation properties, such as asbestos sheet, and be employed with or without the intermediate layer of bulk insulating material 32.

It will be observed that the heat and/or flames from burner 22 are maintained and/or diverted out of direct impingement on the under surface of the bottom crown sheet l4 and that transfer of heat from the burner 22 to the liquid or water within the tank 1%- is devoid of direct application of heat against the exterior surface of bottom crown sheet 14-.

Extensive laboratory tests conducted on the bottom insulated tank structure of FIG. 1, and having Varying amounts of loose insoluble deposits in contact with the interior surface of the crown sheet 14, resulted in complete absence of vapor formation below the deposits referred to, thus eliminating complained of objectionable rumbling noises in the closed hot water system.

Practice of the invention has been equally successful in the closed hot water system and tank structure illustrated in PEG. 2. Similar reference numerals have been employed in FIG. 2 to identify those portions of the system illustrated therein which are identical to the structure of FIG. 1'.

It will be observed that the tank structure of KG. 2 incorporates a central flue dd extending throughout the depth of the storage tank. The bottom end deflector shell 26 in the case of FIG. 2 is provided with a central upwardly flanged opening 32 in registry with the central flue 4h, but is otherwise similar to the structure illustrated in FIG. 1.

FIG. 3 illustrates a modified construction as applied to the bottom crown sheet of elevated temperature liquid storage tanks capable of substitution for the holding tanks illustrated in FIGS. 1 and 2. In F313. 3, the bottom end closure plate or crown sheet a l presents a relatively flat interior and exterior surface. It may be riveted or weld-ed to the cylindrical body portion of a storage tank, or it may be drawn integrally therewith. In other respects, the bottomv end closure crown sheet 44 of FIG. 3 is provided with a pan-shaped shell 43, flanged upwardly at 59 and supported in spaced relationship to the tank body to permit the use of suitable bulk insulation 52. within the intervening space. Otherwise the burner 22 is employed with the tank structure illustrated in FIG. 3.

it will be appreciated by those skilled in the art to which the present invention appertains that the bottom deflector shells 26 and serve to lower the interior temperature of the end closure crown sheets of the liquid storage tanks beneath the loose insoluble deposits supported thereon below the boiling point corresponding to the minimum pressures on the systems.

Normally employed thermal insulation such as glass wool, or the like, and the usual surrounding shells enclosing the same, have been stripped from the storage tanks illustrated hereinabove in the interest of simplifying the illustrations.

it will also be understood that interruption of direct exposure and/or impingement of heat against the exposed exterior surfaces of end closure crowns in normally under-tired storage tanks in elevated temperature liquid systems, such as closed hot water systems, could be a complished by the use of structural heat deflectors other than the spec panshaped shells as d8, illustrated and described he inabove, without departure from the intended scope of invention. However, and in this regard, it is essential to the su cessful practice of the invention that the under-fired hea ng source be so controlled, as by deflection, insulation, or the like, that the interior surface temperatures of the ad closure crown sheets 14 never exceec. the norr -al .ling points of the lid the storage ta. is corresponding to the i'mmurn pressures developed within the systems over their normal ranges. For example, if the minipressure in a water heating system under normal calculated to be twenty pounds per square m ximum temperature of the interior surface of the crown sheet supporting loose insoluble deposits should not exceed 258 F.

Having fully described and illustrated several embodiments of the invention, what is claimed is:

1. In a closed elevated temperature liquid heating system comprising a liquid storage tank and a directly fired end closure crown sheet supporting a layer of loose insoluble deposits accumulated in the liquid within the closed system, said system having an audible noise level of operation in response to flash vaporization of liquid beneath the layer of loose insoluble deposits during pressure drop in the closed system below the rated capacity thereof in the absence of the insoluble deposits, the improvement comprising a heat deflecting means disposed between the exposed bottom surface of the end closure crown sheet and its direct firing means, said heat deflecting means comprising a marginally flanged pan spaced from the exposed bottom surface of the end closure crown sheet and having its marginal flange spaced from the exposed side wall of the storage tank and extended upwardly less than the axial length thereof, and an insulating material confined between the exposed bottom surface of the end closure crown sheet and exposed side wall of the storage tank and the heat deflecting pan, whereby the said system is operational at rated capacity in the absence of audible rumbling noise.

2. In a closed elevated temperature liquid heating system comprising an axially open center flue liquid storage tank and a directly fired end closure crown sheet supporting a layer of loose insoluble deposits on the liquid side thereof accumulated in the liquid within the closed system, said system being characterized by an audible noise level of operation in response to flash vaporization of liquid entrapped beneath the layer of insoluble deposits during pressure drop in the closed system below its rated capacity in the absence of the insoluble deposits, the improvement comprising heat deflecting means interposed the direct firing means and exposed bottom surface of the end closure crown sheet in opposite interior supporting contact with the layer of insoluble deposits, said heat deflecting means comprising a generally pan-shaped member having a contiguous marginal upwardly extending flange sur rounding the exterior wall of the storage tank and a second upwardly struck contiguous flange extending unobstructively into the central flue, said pan-shaped member being spaced from adjacent exposed surfaces of the end closure crown sheet and exterior wall of the storage tank and having the marginal flange thereof extending upward- 1y along the axial length of the exposed exterior wall of the storage tank a distance at least coincident with the maximum depth of the layer of insoluble deposits supported on the liquid side of the end closure crown sheet, and bulk insulating material Within the space between the pan-shaped heat deflecting means and adjacent exposed surfaces of the storage tank, whereby the said system is operational at rated capacity in the absence of audible rumbling noise level.

References Cited in the file of this patent UNITED STATES PATENTS 1,016,959 Sadtler Feb. 13, 1912 1,089,664 Osada Mar. 10, 1914 1,576,563 Wellman Mar. 16, 1926 1,899,523 Ott et al Feb. 28, 1933 2,504,092 Thomas Apr. 11, 1950 FOREIGN PATENTS 281,430 Great Britain Dec. 8, 1927 

